Field of the Invention
Aspects of the present invention generally relate to a developer container, a developing device, a process cartridge, and an image forming apparatus. In the present specification, the image forming apparatus includes, for example, an electrophotographic copying machine that forms an image on a recording material using an electrophotographic image forming process. Moreover, the image forming apparatus includes, for example, an electrophotographic printer, such as a laser beam printer and a light-emitting diode (LED) printer, and a facsimile apparatus.
Description of the Related Art
Japanese Patent Application Laid-Open No. 2002-196585 discusses an image forming apparatus in which an agitation conveyance member that conveys a developer contained in a developer container, which is detachably attached to the inside of the image forming apparatus, toward a developing roller while agitating the developer is mounted inside the developer container. In the image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2002-196585, a plurality of agitation conveyance members is used.
Furthermore, Japanese Patent Application Laid-Open No. 59-227618 discusses a conveyance apparatus for particulates that includes a bearing member for particulates, which is swingably supported, and a vibration generation device, which applies vibration to the bearing member, and that conveys particulates borne by the bearing member by vibrating the bearing member.
However, in the image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2002-196585, the agitation conveyance member conveys only a developer situated within the radius of rotation of the agitation conveyance member. Therefore, the bottom surface of the developer container needs to be formed in a circular arc shape in cross section. For example, a protrusion is formed on a floor surface of the developer container that the agitation conveyance member is unable to reach, in such a manner that any developer does not stay on the area of the protrusion. Since the protrusion becomes a dead space, the volume to contain a developer may decrease.
Furthermore, in the conveyance apparatus discussed in Japanese Patent Application Laid-Open No. 59-227618, a space within which the entire bearing member swings needs to be secured. The space also becomes a dead space.
In order to reduce a dead space on the conveyance route for a developer, it is conceivable that a plate-like conveyance member can be swung along the developer conveyance direction at reciprocating accelerations to convey a developer situated on the plate-like conveyance member.
In the case of vibrating the plate-like conveyance member to convey a developer situated on the plate-like conveyance member, the developer may be oversupplied or undersupplied to a developer bearing member depending on the condition of vibration. As a result, a reduced density or a blank area may occur on a toner image formed on the recording material.
The reason for this is described with the use of a comparative example illustrated in FIG. 14 as follows. FIG. 14 is a sectional view illustrating the configuration of a process cartridge B serving as a comparative example, in which a developer conveyance plate 14b, which constitutes the bottom surface of a developer container 14, is vibrated alternately in a developer conveyance direction J1 and in a developer counter-conveyance direction J2, so that a developer situated on the developer conveyance plate 14b is conveyed.
Referring to FIG. 14, a developer in the developer container 14 is conveyed by the vibration of the developer conveyance plate 14b toward a developing roller 10d, which serves as a developer bearing member, in the developer conveyance direction J1, and is then supplied to the developing roller 10d in a developing chamber 10i. 
At this time, the amount of a developer (a developer amount) in the developing chamber 10i and a powder pressure of the developer, which is powder, greatly influence the performance of supply of a developer that is supplied to the developing roller 10d. If the powder pressure of the developer continues being high with the developer amount in the developing chamber 10i becoming excessive, particles of the developer may be aggregated so that the developer cannot exert the fluidity for particulates.
As a result, although a developer present near the surface of the developing roller 10d is supplied to the developing roller 10d, a subsequent developer is hard to be moved and supplied to the developing roller 10d due to the insufficient fluidity, so that it becomes difficult to keep a good state of supply of a developer to the developing roller 10d. If the supply of a developer to the developing roller 10d stagnates, the amount of a developer borne on the surface of the developing roller 10d may become insufficient, so that a reduced density or a blank area, in which an image is left white, may occur on a toner image formed on the recording material 2.
Furthermore, even in a case where the developer amount in the developing chamber 10i is too small, the amount of supply of the developer to the developing roller 10d may also become insufficient.
In this way, the developer amount in the developing chamber 10i and the powder pressure of the developer greatly influence the performance of supply of the developer to the developing roller 10d. Then, the developer amount in the developing chamber 10i and the powder pressure of the developer are determined by the inflow velocity Vi of a developer that flows into the developing chamber 10i and the outflow velocity Vo of a developer that flows out from the developing chamber 10i. If the inflow velocity Vi and the outflow velocity Vo meet the relationship indicated by the following mathematical expression (1), the developing chamber 10i is in an excessive inflow state in which the amount of a developer that flows into the developing chamber 10i is larger than the amount of a developer that flows out from the developing chamber 10i. At this time, the developer amount in the developing chamber 10i increases and the powder pressure of the developer rises.Vi>Vo  (1)
On the other hand, if the inflow velocity Vi and the outflow velocity Vo meet the relationship indicated by the following mathematical expression (2), the developing chamber 10i is in an excessive outflow state in which the amount of a developer that flows out from the developing chamber 10i is larger than the amount of a developer that flows into the developing chamber 10i. At this time, the developer amount in the developing chamber 10i decreases and the powder pressure of the developer lowers.Vi<Vo  (2)
Ideally, if the inflow velocity Vi and the outflow velocity Vo meet the relationship indicated by the following mathematical expression (3), both the developer amount in the developing chamber 10i and the powder pressure of the developer can be kept into an appropriate state, so that the supply state of the developer to the developing roller 10d can also be kept always appropriate.Vi=Vo  (3)
As illustrated in FIG. 14, the developer in the developer container 14 is conveyed in the developer conveyance direction J1 by the vibration of the developer conveyance plate 14b and is then supplied to the developing roller 10d in the developing chamber 10i. The developer borne on the surface of the developing roller 10d is consumed by image formation. Thus, the developer in the developing chamber 10i sequentially decreases for each image formation.
The factor affecting the inflow velocity Vi of a developer that flows into the developing chamber 10i includes, for example, a vibration condition of the developer conveyance plate 14b and a conveyance performance of the developer itself. On the other hand, the factor affecting the outflow velocity Vo of a developer that flows out from the developing chamber 10i includes, for example, a coverage rate (printing ratio) of a toner image to be formed on the recording material 2.
In a case where the developer conveyance plate 14b is set to a predetermined vibration condition, if the outflow velocity Vo of a developer that flows out from the developing chamber 10i and the conveyance performance of the developer itself do not vary, there is no problem. However, actually, the coverage rate of a toner image to be formed on the recording material 2 varies for each print job, and the conveyance performance of the developer itself also varies with repetition of use. Therefore, in a case where the vibration condition of the developer conveyance plate 14b is fixed, it is difficult to keep always optimum the balance between the inflow velocity Vi of a developer that flows into the developing chamber 10i and the outflow velocity Vo of a developer that flows out from the developing chamber 10i. 